During the course of a flight, a pilot receives many uplinked messages from an air traffic controller depending on different parameters and conditions. The controller basically sends any required data to the aircraft to fly in a safer zone. For example, the controller can ask the pilot to fly the aircraft at a particular altitude, speed, heading, or the like. Such constraints defined by the controller are uplinked through datalink communications, and are then inserted or loaded into the active flight plan in the aircraft.
When an air traffic control (ATC) uplink message is sent to an aircraft, the uplink message is statically validated (format, range of values, etc.) and may be loaded automatically when received or after acceptance by the pilot, depending on the aircraft system architecture. In some cases, loading can include a flight plan system static validation such as by a flight management system (FMS). After the uplink message is accepted, an acknowledgement indicating acceptance is sent to the controller. As the pilot can load an uplink message at any point after acceptance, any elapsed time can change the conditions applicable to the uplink message.